Biosynthesis of Haem 



I would like now to refer to some experiments which a group* in 

 London of which I am a member have carried out with the Coryne- 

 bacterium diphtheriae as the synthesizing system. This organism has 

 long been known to produce porphyrin in its culture fluid and 

 Ch. Gray and L. B. Holt 13 have characterized the pigments as 

 mainly coproporphyrin III together with a small quantity of uropor- 

 phyrin I and traces of an unidentified porphyrin. We have succeeded 

 in growing the organism on a purely synthetic medium with good 

 yields of pigment. As is well known, the quantity of iron in the 

 medium greatly affects both porphyrin and toxin production. With 

 minimal iron, the porphyrin production is high, that of intracellular 

 haems low and with abundant iron these proportions are reversed. 

 W. A. Rawlinson and J. H. Hale 14 have examined the intracellular 

 haems and find the greater part to be ferriprotoporphyrin IX, 

 identified with the prosthetic group of cytochrome b, but there is also 

 present a dichroic haem somewhat resembling chlorocuoro (spiro- 

 graphis) haem, which they consider to be the prosthetic group of the 

 a cytochromes. 



Our runs were performed with high and low iron and normal and 

 N 15 labelled glycine. The results are shown in Table I. 



Table I 

 Utilization of N-Labelled Glycine by C. Diphtheriae 



Atom % excess N 15 



/ Normal glycine 

 Low Fe J I so topic glycine 

 (5-584 atom % 

 \ excess) 



/Normal glycine 

 High Fe 1 1 so topic glycine 

 (5-584 atom % 

 excess) 



Bacterial 

 cellti 



Intra- 

 cellular 

 haem N 



Copropor- 

 phyrin N 



* Hale, J. H., Rawlinson, W. A., Gray, Ch., Holt, L. B., Rimington, C, Smith, W. 



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